Taxonomic discussion: The globigerinathekids display an enormous amount of morphological variability in features such as test size and the number, shape and size of secondary apertures. The complexities surrounding the genus Globigerinatheka are best summarized chronologically.1952 - Bronnimann (1952) erected the genus Globigerinatheka comprising only the new species G. barri, the type species. He characterized the genus as having an almost spherical trochospiral test with four chambers in last whorl and “composite supplementary chambers, consisting of a single large inflated primary chamber across the umbilicus and of three small, only slightly inflated secondary chambers” (structures that are recognized here as bullae), with multiple (maximum of nine), small semicircular apertures in secondary chambers.1957 - Bolli and others (1957) erected the genus Globigerapsis, with the new species G. kugleri as the type species, to accommodate subspherical forms similar to the genus Globigerinatheka but devoid of bullae covering the secondary apertures. These authors included in the new genus the species Globigerinoidessemiinvoluta Keijzer and a specimen identified by Bermudez (1949) as Globigerinamexicana Cushman that, according to them, may be closer to semiinvoluta. In the same paper Bolli and others (1957) also erected the genus Porticulasphaera, with Globigerinamexicana Cushman as the type species, which differed from Globigerapsis “in having the Globigerinoides-type of secondary apertures on the spiral side in the early coil.”1962 - Saito (1962) observed that the description of Porticulasphaeramexicana by Bolli, Loeblich andTappan (1957) did not correspond to the characters of the mexicana holotype, and re-named the Bolli, Loeblich and Tappan species Porticulasphaerabeckmanni; in addition he included the true mexicana in the genus Globigerapsis.1968 - Blow and Saito (1968a) re-examined and re-illustrated the holotype of G. mexicana and reiterated that Cushman’s species belonged to the genus Globigerapsis. They stated also that the species mexicana is similar and conspecific with Globigerapsissemiinvoluta (Keijzer), which they consequently considered a junior synonym of G. mexicana, a synonymy rejected here and also by Bolli (1972). These authors also erected the new genus Orbulinoides for Saito’s species beckmanni, invalidating the genus Porticulasphaera due to a misidentification of type species. However, the new combination Orbulinoidesbeckmanni was published a few months earlier by Cordey (1968), who became the author of the genus Orbulinoides (see the discussion below under Orbulinoides).1970 - Proto Decima and Bolli (1970) observed that all the species included in the genus Globigerapsis may possess bullae. Consequently, this made the genus Globigerapsis a junior synonym of Globigerinatheka. These authors also revised and emended the genus Orbulinoides, which is characterized by possessing numerous sutural supplementary apertures that in the early stage open into vestibules, the thick wall of which has separate apertures. It also has few areal apertures in the last, large enveloping chamber, and some irregular bulla-like structures (see below).1972 - Bolli (1972) revised the genus Globigerinatheka in which he distinguished four morphologically distinct species, containing 12 subspecies, as follows:1) Group ‘mexicana’, characterized by small size, a more or less globular test and frequent bullae, that includes mexicanamexicana, mexicanabarri, mexicanakugleri.2) Group ‘subconglobata’, characterized by a large (except micra) globular test size, robust walls and occasional bullae, that includes subconglobatasubconglobata, subconglobata micra, subconglobatacurryi, subconglobataeuganea, subconglobataluterbacheri. According to Bolli (1972), the subspecies curryi is the first member of the lineage leading to “beckmanni” via euganea, in the process changing the test outline from subtriangular in curryi to almost circular in euganea, initially with 3 chambers in the last whorl. Further changes include an increase in the length of the somewhat flat initial spire and increases in the size of the last chamber and in the degree of chamber envelopment.3) Group ‘index’, characterized by an elongate test shape and apertures that are usually not covered by bullae, that includes indexindex, indexkorotkovi, indextropicalis and indexrubriformis.4) G. semiinvoluta, characterized by an almost spherical test with short flat inner spire and a well-developed hemispherical last chamber with more or less large circular openings.1979 - Blow (1979) re-emended the three genera Globigerinatheka, Porticulasphaera and Globigerapsis and attributed the species previously mentioned as follows:1) Globigerinatheka, monotypic, including only the type species barri, characterized “by consistently possessing true bullae covering the supplementary apertures of the last chamber”, “in having a long earlier trochospiral stage in ontogeny” with streptospiral coiling mode affecting only the last two chambers, and a wall “of normal globigerinacean type”, bearing “normal long, acicular, spines” without murical sheath.2) Porticulasphaera, characterized by a rather short trochospiral stage, a large last chamber that “may embrace a considerable part of the earlier test”, a normal globigerinacean type, non-muricate wall and apparently without bullae. It includes two subgroups:A – mexicana, including mexicanamexicana, senior synonym of tropicalis, here considered as a discrete taxon, and mexicana howei, here considered to belong to the genus Catapsydrax,B – semiinvoluta, senior synonym of lindiensis (here lindiensis is considered a junior synonym of G. tropicalis).3) Globigerapsis, characterized by a wall bearing closely packed muricae forming a murical sheath, that may appear as a thickened wall; a streptospiral coiling mode early in ontogeny; multiple sutural secondary apertures in chambers prior to the last one, small areal apertures in some forms and possible presence of small bullae. It includes three subgroups:A – beckmanni,B – index, the intermediate member of the plexus Muricoglobigerinasenni -index -kugleri,C – kugleri, including kugleri kugleri, kugleri curryi, and kuglerieuganea.Blow (1979) also stated that if bullae were not to be considered as having taxonomic importance as well as secondary apertures in earlier chambers, then the species he included in Porticulasphaera “should be transferred to the genus Globigerinatheka”. Conversely, Blow (1979) said that Globigerinatheka has distinctly different ancestry from the genus Globigerapsis and the “gross homeomorphy” of taxa belonging to both genera is “due to phyletic convergent evolution” and transitional forms are lacking. Wall texture studies by our Working Group (Hemleben and Olsson, this volume) have failed to find evidence of Blow’s “murical sheath” structure, and all of the species included by him in Globigerapsis are certainly spinose, hence we do not regard any of the groups as likely descendants of the Acarinina group (which includes Blow’s genus Muricoglobigerina) (see Hemleben and Olsson, Chapter 4, this volume).Concerning the genus Orbulinoides, Blow (1979), in agreement with Proto Decima and Bolli (1970) and Bolli (1972), considered the species beckmanni as the end member of the curryi -euganea lineage, but he assigned it to the genus Globigerapsis with its ancestral forms, saying that it is not necessary to include “beckmanni” in a different genus.1983 and 1985 - Toumarkine (1983) and Toumarkine and Luterbacher (1985) rejected the generic classification of Blow (1979). They retained the genus Globigerinatheka, comprising the groups/lineages identified by Proto Decima and Bolli (1970) and Bolli (1972), and the genus Orbulinoides for the species beckmanni.To summarize, in disagreement with Blow’s (1979) observations, our study demonstrates that none of the species included by him in the genus Globigerapsis possess a muricate wall, but they do have the same wall texture as Globigerinatheka. Thus, lacking any criteria for distinguishing the three genera, the only genus retained here is Globigerinatheka, and both Porticulasphaera and Globigerapsis must be considered junior synonyms of the former. On the other hand, the presence of numerous, closely spaced, sutural secondary apertures as well as few areal apertures (never observed in any of the globigerinathekids; see also Proto Decima and Bolli, 1970), appears to be a valid criterion for keeping Orbulinoides as a separate genus, analagous to the manner in which the Miocene Praeorbulina- Orbulina plexus is distinguished from the genus Globigerinoides.Finally, we discuss Globigerinaorbiformis Cole, 1927. Under this name Cole (1927) described, and poorly illustrated, a spherical form with small supplementary apertures and smaller than mexicana (about half the size), with a rougher surface, that he regarded as the ancestor of Cushman’s G. mexicana. From our SEM photographs of the type series, the four paratypes all share a strongly cancellate wall, with most diagnostic features masked by strong recrystallization. The general shape varies from subglobular to sac-like, in the latter case possibly related to a long, rather high spire. There are 3 to 4 chambers in the last whorl; sutures are not visible in most of the test except between the last two chambers where they are slightly depressed; the primary aperture is umbilical in position, with a low wide arch and rough border; secondary apertures were not positively detected in any specimens. This rarely recorded species (a poor drawing was given by Bermu½dez, 1949, and short comments by Hagn, 1956) appears to be closer to Subbotinasenni than to globigerinathekids, as previously suggested by Beckmann (in Bolli, 1972, p. 134).PHYLOGENETIC RELA TIONSHIPS.— As observed by Proto Decima and Bolli (1970) and Bolli (1972), the globigerinathekids display morphological similarities or differences at the species level concerning the length and growth rate of the inner spire, and the size and enveloping degree of the last chamber. These allow us to suggest possible phylogenetic relationships and are reported in the description of each species and graphically plotted in Figure 7.1.The first globigerinathekid to evolve was Globigerinathekasubconglobata, which has been positively indentified in the middle part of the lowermiddle Eocene, Zone E8. The appearance of true globigerinathekids was preceded by the presence of morphotypes without secondary apertures and/or bullae that suggest a relationship with Guembelitriodes nuttalli, with which they share a similar cancellate, spinose wall texture (see the introduction to this chapter and Plate 7.1). G. subconglobata apparently gave rise over a very short time span to several other globigerinathekids in Biochron E9.The first species to evolve after G. subconglobata was the subtriangular shaped G. kugleri which, in agreement with Blow (1979), is considered to be the ancestral member of the G. curryi -Orbulinoidesbeckmanni lineage, which evolved via G. euganea (see Bolli, 1972), the transition being characterized by the progressive increase in the enveloping degree of the last chamber, accompanied by the increase in length of the inner spire, eventually producing the spherical shape of Orbulinoidesbeckmanni; G. luterbacheri appears to branch off independently from G. euganea in E12.At the same time, a second morphologic transition occurred, also characterized by the increase in streptospirality and of the degree of embrace of the final chamber, leading to a subspherical outline. In this way, G. mexicana branched off from G. subconglobata. The former developed a much larger last chamber, which strongly embraces the previous whorls, and probably gave rise to its end member G. semiinvoluta in the latest middle Eocene. Even though several authors considered G. barri as closely related to G. mexicana, it is more likely that G. barri descended independently from G. subconglobata.Within E9, a third evolutionary trend in Globigerinatheka occurred, in which the 4-chambered subglobular outline of G. subconglobata evolved to be more rectangular with basically three chambers in the last whorl. This gave rise to the high-spired G. korotkovi, and independently to the subrectangular G. index with incised sutures in late E9. We consider G. index to be ancestral to G. tropicalis, which appears in mid Zone E13. [Eocene Atlas]

NB These concise distinguishing features statements are used in the tables of daughter-taxa to act as quick summaries of the differences between e.g. species of one genus.They are being edited as the site is developed and comments on them are especially welcome.

Biogeography and Palaeobiology

Biostratigraphic distribution

Geological Range: Notes: Globigerinathekids range from the lower middle Eocene Zone E8 (=P10) to around the Eocene/Oligocene boundary. [Premoli Silva et al. 2006]Last occurrence (top): in upper part of Priabonian Stage (80% up, 34.7Ma, in Priabonian stage). Data source: Total of range of species in this databaseFirst occurrence (base): in lower part of Lutetian Stage (32% up, 45.7Ma, in Lutetian stage). Data source: Total of range of species in this database